Immunology Flashcards
What is the difference between an allergy and intolerance?
Allergy –> immune reaction usually IgE mediated
Intolerance –> non immune reaction
What tests do you offer to determine a food allergy?
Blood tests for IgE mediated antibodies
THEN Skin prick test or prick-prick test
Why should things like skin prick test, food challenges and atopy patch testing not be done in a primary healthcare or community setting?
Risk of anaphylaxis
If individual DOES NOT have IgE mediated food allergy, what should be done next?
Eliminate suspected allergen for 2-4 weeks, then reintroduce
If a child has cow milk allergy, what advice should be given?
Advice on food avoidance to breast feeding mothers
Info of appropriate hypo-allergenic formula or milk substitute to mother of formula fed babies
When should referral to secondary healthcare be considered in terms of a food allergy?
No response to diet removal of allergen
Child has confirmed IgE food allergy and concurrent asthma
Tests are negative but still strong suspicion of IgE food allergy
What are the 4 immunologically-mediated reactions of drug eruptions?
type I: anaphylactic
type II: Cytotoxic reactions
type III: Immune complex mediated reactions
type IV: T Cell-mediated delayed hypersensitivity reactions
Are immunologically-mediated reactions dose dependent?
No
Are Non-immunologically-mediated reactions dose dependent?
Can be
What is the most common presentation of drug eruption rash?
Exanthematous
What is the second most common presentation of drug eruption rash?
Uticaria
What kind of immunologically mediated reaction is a Exanthematous drug eruption?
Type IV
What are the signs and symptoms of a exanthematous drup eruption?
Wide spread, symmetrical rash Mucous membranes usually spared e.g. mouth Pruritis Mild fever Onset 4-21 days after first taking drug
What are the indicators of potential, severe reaction?
Involvement of mucous membranes and face Facial oedema and erythema Widespread confluent erythema Fever >38.5 Blisters, purpura, necrosis - sloughing of the skin Lyphadenopathy Arthalgia SOB, wheezing
What drugs are associated with exanthematous
Penecillins NSAIDs Erythromycin Phenytoin Anti-Epileptics Allopurinol
What drugs can cause Acute Generalised Exanthematous Pustulosis (AGEP)
Antibiotics
Ca channel blockers
Antimalarials
What drugs can cause drug induced Bullous Pemphigoid?
ACE inhibitors
Penecillin
Furosemide
What drug can cause Linear IgA bullous disease?
Vancomycin
What medications can cause a fixed drug eruption?
Tetracycline, Doxycycline
Paracetamol
NSAIDs
Carbamazepine
What is Steven-Johnsons Syndrome?
Stevens–Johnson syndrome, a form of toxic epidermal necrolysis, is a life-threatening skin condition, in which cell death causes the epidermis to separate from the dermis. The syndrome is thought to be a hypersensitivity complex that affects the skin and the mucous membranes.
What is Toxic Epidermal Necolysis?
The disease causes the top layer of skin (the epidermis) to detach from the lower layers of the skin (the dermis), all over the body, leaving the body susceptible to severe infection. Death usually due to sepsis or multiorgan system failure
What is Acute Generalised Exanthematous Pustulosis?
Uncommon skin eruption. It is characterised by the rapid appearance of areas of red skin studded with small sterile pustules (small blisters filled with white/yellow fluid). There tend to be more disease in skin folds. Facial swelling often arises.
Drugs associated with phototoxicity?
Antibiotics (fluroquinolones, tetracyclines) Thiazide diuretics Amioderone Immunosuppresents Antifungals
What are the two kinds of immune response?
Innate and Adaptive
What is the innate immune response?
Non specific, no memory, first line defence
What is the adaptive immune response?
Memory. highly specific, tolerance and self limiting
Definition of an antigen
A protein/peptide or polysaccharide that elicits a immune response
What activates Keratinocytes?
UV
Sensitizers
Once activated, what do kertainocytes produce?
Antimicrobial peptides (AMPs) that can directly kill pathogens
Cytokines
Chemokines
Is what disease are many antimicrobal peptides found on the surface of the skin?
Psoriasis
What granule characterises a Langerhans cell?
Birbeck granule (looks like a tennis racket)
What do Langerhans cells do?
They process lipid Ag and microbial fragments and present them to effector T cells. They help activate T cells
Which T cell is mainly found in the epidermis?
CD8+ T cells
What T cells are found in the dermis?
CD4+ and CD8+
What do CD4+ cells do?
Send out cytokines which direct and instruct other cells to kill
What do CD8+ cells do?
Kill infected cells directly
Where are T cells produced?
Bone marrow
Where do T cells mature?
Thymus
What does CD4+ cells produce?
TH1 and TH2
What dos TH1 do?
Activates macrophages to destroy microorganisms
IL2, TNF
What dos TH2 do?
Helps B cells to make Ab IL4, IL5, IL6
What different kinds of dendirtic cells are found in the dermis?
Dermal DC
Plasmacytoid DC
What do Dermal Dendritic cells do?
Involved in Ag presenting and secreting cyto/chemokines in inflammation
What Plasmacytoid dendritis cells do?
Produce IFNa found in diseased skin
What cells transmit information to T and B cells
Antigen presenting cells –> Dendritic cells
What immune defence cells are found in the dermis?
Dendritic cells
Macrophages
Neutrophils
Mast cells
Which immune defence cells are the effectors of the IgE mediated immune response (allery) ?
Mast cells
What causes mast cells to release inflammatory mediators?
Binding of IgE onto the surface of the mast cell
What preformed mediators do mast cells contain?
Histamine
TNF
Chymase
Tryptase
What triggers psoriasis?
Environmental factors in genetically susceptible people e.g. stress, trauma
What is Koebners phenomenon?
Lesions appear at site of an injury e.g. in psoriasis
What parts of the body does psoriasis affect?
Skin
Nails
Joints
What medications can aggravate psoriasis?
Beta blockers
Lithium
What happens to melanocytes in Vitiligo?
The melanocytes are attacked by T cells
Which hypersensitivity reaction is IgE mediated?
Hypersensitivity Type I
What does hyposensitisation treatment do?
Make body produce IgG when exposed to allergen
What hypersensitivity reaction is IgG mediated?
Type II
If you were to do a skin test, what response would hypersensitivity type III give?
Arthus reaction (slow than TI but faster than TIV)
Which hypersensitivity is deemed a “allergy”
Type I
Which hypersensitivity is important in certain drug reactions?
Type III
Which hypersensitivity is TH1 mediated? (t cell mediated)
Type IV
Which hypersensitivity gives a delayed response?
Type IV
Definition of hypersensitivity
Immune response that causes collateral damage to self
Which hypersensitivity is immune complex mediated?
Type III
What type of hypersensitivity is contact dermatitis?
Type IV
What type of hypersensitivity is graft rejection?
Type IV
What type of hypersensitivity is rheumatoid arthritis?
Type III
What type of hypersensitivity is anaphylaxis?
Type I
What test is performed in anaphylaxis?
Serum mast cell tryptase level
How do you treat anaphylaxis?
Adrenaline
How to treat allergic reaction?
Avoidance Anti-histamines Steroids (for inflam) Sodium cromoglycate (Blocks mast cell activation) Allergy bracelete Immunotherapy Eduaction
How much adrenaline do you give to children in anaphylaxis?
150ug
How much adrenaline do you give to adults in anaphylaxis?
300ug
How many adrenaline pens should someone with potential anaphylaxis be given?
2
How long is the onset of symptoms for type IV hypersensitivity ?
24-48 hours
Patient has long history of well demarcated eczematous rash near umbilicus, what is the likely diagnosis?
Nickel allergy due to belt
44 yr old surgeon with eczematous rash on hands extending to his forearms, what is the diagnosis?
Thiuram allergy (rubber accelarator) in nitril gloves
Eczematous rash under both axilla, what is the diagnosis?
Deodorant allergy –> axillary dermatitis
Chef comes in with first 3 fingers of left hand with red, itchy and dry skin. What is the likely diagngosis?
Garlic allergy
Scuba diver comes in with whole body covered in eczematous rash, what is the likely diagnosis?
Diethylthiourea allergy, found in wet suits
Teen comes back from holiday with a henna tattoo. Henna tattoo starts to get, peely and sore. What chemical is causing this?
PPD
Child has marks all around lips, what is this most likely due to?
Lip lick dermatitis, skin reacting to with saliva
Management of dermatitis?
Allergen/ irritant avoidance Allergen/ irritant minimisation Emollients Topical steroids UV phototherapy Immunosuppresants
What advice would you give someone with allergy to fragrances?
use hypallergenic brand or baby brands